M Shuts Off No Spark

[SuperABen]

My 1948 M has decided to act up a bit.

It was completely redone a few months ago. It hasn't seen much hard work since, although I have used it to drag another tractor or two around the yard.

A few days ago it sat outside for an hour, not running, while I pulled another tractor out. When I went to start the M, it ran for a minute and then cut off just like someone hit the switch. I checked for spark (after a few other things) and I had nothing. I had 6 volts to the coil, though. The only thing I didn't check was spark straight from the coil terminal. The next morning it started right up and gave me a good days work shuttling trailers.

Yesterday I started it up for a customer, and I noticed that when it was idling, I could see a flash of a spark coming from the spark plug boot to the cylinder head. After he left, I checked for a rub (on a new wire set??) and didn't see a thing.

Tonight I pulled it out again, and it had 100% power. However, while rolling down the road in full throttle at road gear, it cut off. No spluttering, acts like something hit the switch. Once again, full power to the coil. No spark.

It started up again in about 15 minutes, ran well for a minute, began spitting and carrying on, backfiring, and the whole works. Then it died straight off at full throttle. That's the first time it did that.

I'm at ignition right now. I'm stumped because the distributor (Delco) has everything new. Spark plugs, wires, distributor cap, rotor, condenser, points, wires to and from coil, coil itself, wires to switch, etc.

I'm assuming a bad connection. Before I rip this character apart again, has anyone seen something similar with all new parts?

Ben W.

 

[James Howell]

We've got a 51MT "Rusty" that occasionally acts up like you have described.

You might consider changing the condenser; that has solved the problem each time on "Rusty".

For some reason that tractor goes through a condenser about every six months.

Hope this helps.

 

[M-MAN]

I would change the plug wires first because you know they are bad.(use solid core) Pull the dist stud and check the insulator. Then put your old condenser back in if it still acts up.

 

[MEANJDK]

Whether its the correct fix or not, do consider an electronic ignition upgrade.
I have always had problems like yours for years, since the upgrade, NO problems now.
Mine is original 6v, POS ground.
Im beginning to beleive the little M tractors are OK.

 

[leon]

My MT let down about like that a couple of years ago while on a tractor ride. It was sort of embarrassing to be pulled in by a red tractor! The problem turned out to be an extreme amount of corrosion inside the boot of the high tension center lead coming off the coil. With that coil being mounted "upside down", it's a good place for water to accumulate and then rust/corrode.

 

[Hotflashjr]

Mine was doing the same and I needed a condensor. Some of the new ones out there are kinda cheaply made and do not seem to last long. The first one I bought only lasted about 6 months like James described. I was lucky enough to find a NOS one and that has been in there about two years now.

 

[SuperABen]

Thanks to everyone for their replies. I went out on a limb and threw a part at the distributor: the condenser seems to have been the issue. It ran for a good 30 minutes tonight without a problem.

Ben W.